1. Field of the Invention
This invention relates to room temperature vulcanizable organopolysiloxane compositions which are readily vulcanizable with moisture in the air to form rubbery elastomers having improved water immersion and thermoresistant adhesion.
2. Prior Art
Room temperature vulcanizable (RTV) organopolysiloxane compositions which readily cure with moisture to form rubbery elastomers are well-known in the art. They are widely used in a variety of fields as adhesives, coatings, electrically insulating sealants, and building sealants because the cured elastomers have excellent characteristics including weather resistance, durability and freeze resistance.
Recently, acryl resin and fluoro-resin electrodeposited aluminum members featuring weather resistance and having a less adhesive surface have been utilized as building exterior materials. RTV organopolysiloxane compositions do not firmly bond to such aluminum members surface coated with acryl resins and fluoro-resins. The organopolysiloxane compositions applied to the surface coated aluminum members also suffer from the problem that they become peeled when immersed in water for a long time.
Known RTV organopolysiloxane compositions are often loaded with calcium carbonate as a filler. For example, JP-A 39422/1993 discloses the use of calcium carbonate which has been treated with 3% by weight of a treating agent in the form of rhodinic acid. The use of calcium carbonate as a filler is also proposed in JP-A 179760/1995 and U.S. Pat. No. 5,405,889 (issued Apr. 11, 1995). Allegedly these compositions are also improved in anti-spitting and adhesion. These compositions, however, are not satisfactory in water immersion and thermoresistant adhesion to less adhesive surface coatings on aluminum members and mortar.
It was proposed by Dow Corning Toray Silicone Co. to use a filler blend of calcium carbonate treated with stearic acid and fumed silica. In water immersion and heating tests, however, the stearic acid on the surface of calcium carbonate leaches out to adversely affect the adhesion. This proposal is thus not satisfactory in performance.